Is knowing the Blender internal renderer settings for materials and textures important for using the Cycles renderer?
Short answer: nope.

Cycles and BI work very differently, consequently materials are completely different for the two, both in the way they are defined and calculated.  I think learning BI first often does more damage than good when switching to Cycles.

I should note that some people do say new users should start with BI since it is (arguably) simpler than Cycles.  I heartily disagree with this view though.  Cycles may be a little more complex to some people due to it's much greater flexibility, but I don't see any reason why starting with BI would help one learn Cycles.

I think the idea that BI is "simpler" is a misnomer though, it's just different.  Personally, I find Cycles's nodes to be a much more intuitive way of defining materials than BI's wall of settings for everything under the sun.  Which one really is simpler is a matter of opinion, so neither one comparatively blows the other out of the water and should.